矿渣对高镁水泥硬化浆体膨胀特性及微观结构的影响

MgO可用于补偿大体积混凝土的收缩，大坝混凝土中也已有应用高镁水泥的先例。为充分利用高镁水泥的膨胀特性，避免其膨胀量过大，本文研究了矿渣掺量和细度对其膨胀特性的影响，并表征了硬化浆体的孔结构与微观形貌。结果表明，掺入矿渣可以有效降低高镁水泥硬化浆体的膨胀率。矿渣的掺量越高，硬化浆体膨胀率越低。矿渣的细度越细，抑制硬化浆体膨胀的作用越明显，中位径为4．81μm时，硬化浆体膨胀率显著降低。矿渣抑制高镁水泥硬化浆体膨胀的作用，主要源于矿渣掺入之后所产生的“物理稀释作用”和“二次水化效应”。“物理稀释效应”降低了硬化浆体中方镁石总量；“二次水化效应”填充了硬化浆体空隙，使硬化浆体孔径细化，毛细孔缓冲和释放硬化浆体膨胀应力。

Effects of Slag on the Expansion Characteristic and Microstructure of Hardened Cement Past with High MgO Content

MgO could be used to compensate the shrinkage of mass concrete, and cement with high MgO content has been applied in dam concrete. In this paper, cement with 10% MgO was prepared, the effects of the dosage and the fineness of slag on the expansion characteristics of hardened cement pastes were studied, and the pore structure and microstructure of hardened cement pastes were characterized. The results indicated that the expansion rate of hardened cement paste decreased with the addition of slag. The expansion rate of hardened cement paste decreased with the increase of slag and the decrease of fly ash fineness. The expansion rate decreased significantly when the median diameter of slag was 4. 81μm. The decrease of the expansion rate depended on the “physical dilution effect”, “secondary hydrate reaction” of slag. The pore size reduced with the addition of slag, which resulting in the decrease of the expansion rate.